Extracorporeal shockwave therapy (herein referred to as ‘ESWT’) is non-surgical, non-invasive treatment of medical conditions using acoustic shockwaves. First use of shockwave therapy in the early 1980's was utilized to fragment kidney stones termed shockwave lithotripsy. Continued development of shockwave treatment showed the possibility of stimulating bone formation, angiogenesis, as well as other orthopedic indications. However, medical literature suggests that lithotripsy creates hypertension and some damage to the kidney including hematuria during the procedure.
A shockwave is a form of acoustic energy resulting from phenomena that create a sudden intense change in pressure for example an explosion or lightning. The intense changes in pressure produce strong waves of energy that can travel through any elastic medium such as air, water, human soft tissue, or certain solid substances such as bone.
Shockwaves are characterized by the delivery of a sequence of transient pressure disturbances characterized by an initial high peak pressure with a fast pressure rise followed by rapid wave propagation with diminishing amplitude over its lifecycle. Such that shockwaves characteristically have a quick lifecycle, starting with a big high amplitude pressure peak followed by a gradual diminishing pressure amplitude having amplitude of about 10-20% of the initial pressure peak. Shockwave are further characterized in that they do not produce heat within the tissue.
Shockwaves are therefore characteristically different from ultrasound in that the ultrasound waveform produces constant cyclic sinusoidal amplitude that produces heat at the tissue level. Conversely shockwaves do not have constant amplitude over time.
Acoustic shockwaves are primarily generated by three different methods, electrohydraulic (also referred to as spark gap), electromagnetic (also referred to as ‘EMSE’), and piezoelectric. Each method needs an apparatus to focus the generated shockwave so as to provide a focal point and/or focal zone for the treatment area. In the focal zone shockwaves produce much higher pressure impulses as compared with the zones outside of the focal zone.
Mechanical means for focusing each of these methods is generally realized with an appropriate arrangement of surfaces reflecting the wave toward the desired focal point and/or an appropriate arrangement of the generating devices.
Spark gap systems incorporate an electrode (spark plug), to initiate a shockwave, and ellipsoid to focus the shockwave. EMSE systems utilize an electromagnetic coil and an opposing metal membrane. Piezoelectric systems form acoustical waves by mounting piezoelectric crystals to a spherical surface to provide focus. Of the three systems, the spark gap system is generally preferred in the art for generating therapeutic shockwaves ESWT as it introduces more of the generated shockwave energy to the treatment target site.
In spark gap systems, high energy shockwaves are generated when electricity is applied to an electrode positioned in an ellipsoid immersed in treated water. When the electrical charge is fired, a small amount of water is vaporized at the tip of the electrode and a shockwave is produced. The shockwave ricochets from the side of an ellipsoid and converges at a focal point, which may then be transferred to the area to be treated.
In electromagnetic systems an electrical impulse is circulated in a coil. The coil produces an electromagnetic field that expels a metallic membrane to produce the mechanical impulse.
In piezoelectric systems ceramic material with piezoelectric characteristics is subjected to an electrical impulse. The electric impulse modifies the dimension of the ceramic material to generate the desired mechanical impulse. A focal point is attained by covering a concave spherical surface with piezoelectric ceramics converging at the center of the sphere.
The method of focusing the generated shockwave has been greatly described in the art for example in U.S. Pat. Nos. 5,174,280 and 5,058,569, 5,033,456, EP1591070 all of which are incorporated herein by reference as if fully set forth.
Traditionally shockwaves have been used in medicine as a noninvasive means for treating a variety of anomalies such as kidney stones (lithotripsy), fragmentation of calcification, chronic orthopedic inflammation healing, bone healing (osteogenesis), wound healing, revascularization, angiogenesis are well known and described in medical literature.
U.S. Pat. No. 7,507,213 to Schultheiss, et al. discusses invasive stimulation of kidney by surgically exposing the organ for example heart or kidney prior to applying shockwave therapy.
US Patent Publication No. 2011/0257523 to Hastings et al. discusses a method utilizing high intensity focused ultrasound (HIFU) for ablating innervated tissue of the kidney, for denervating renal vasculature, including disruption and termination of renal sympathetic nerve activity, to improve cardiac and/or renal function particularly that associated with hypertension.